1. Field of the Invention
The invention relates to polyol compositions and rigid polyisocyanate based foams. In particular, the polyol composition and rigid polyurethane foams made therewith are made with a combination of a polyoxyalkylene polyether polyol, 2-chloropropane and a C.sub.4 -C.sub.6 aliphatic hydrocarbon blowing agent.
2. Background of the Invention
The polyurethane foam industry is well under way replacing the ozone depleting chlorofluorocarbons (CFCs) with more benign compounds such as hydrochlorofluorocarbons (HCFCs). However, HCFCs appear to be a temporary replacement; and efforts continue toward a permanent solution by employing blowing agents that have zero ozone depletion potential.
Hydrocarbons are a class of compounds receiving considerable attention as possible permanent solutions to HCFC-blown foams. Advantages of hydrocarbons include a zero ozone depletion potential, a very low global warming potential, and being liquids at more temperature. Hydrocarbons are also inexpensive when compared to HCFCs or hydrofluoroalkanes (HFAs). In addition, the technology for the safe handling of flammable blowing agents in a manufacturing environment already exists in practice. One drawback to hydrocarbons, however, is that they are insoluble in polyols and do not form stable homogenous mixtures. This not only leads to processing complications but also a nonuniform cell density in the foam product. As a result, hydrocarbons must be separately added and vigorously mixed with polyols immediately prior to the manufacture of the rigid foam or injected as a separate stream into a mix head. If one desires to avoid separate addition and mixing the polyols and hydrocarbon immediately prior to foam manufacture, the only other solution currently is to create an emulsion using emulsifiers.